Spacing stick placer apparatus are used to place spacing sticks between stacked tiers of green lumber. The sticks serve to provide space between the tiers of lumber to allow air flow for either kiln drying or air drying, as well as to stabilize the tiered lumber package. Typically, spacing stick placer apparatus are used in conjunction with lumber stackers that stack the green lumber in tiers, the stick placer apparatus conventionally being placed over the lumber stacker. The sticks are placed in spaced parallel array across the width of the lumber tiers, the sticks aligned perpendicular to the long dimension of the lumber. The number of sticks so placed depends upon the length of the lumber and the desired spacing between the sticks. In modern sawmill practices it is desired that the first and last stick of the array of sticks placed onto a tier of lumber be placed flush with the ends of the lumber. It is also desired that a stick placer be able to accomodate lumber of difference lengths.
It is conventional for sticks to be conveyed over the lumber stack from a stick allocating device by means of a continuous chain from which depend spaced apart hooks. The spaced apart hooks are "J" shaped so as to receive and support a single stick per hook. The "J" shaped hooks, hereinafter J-hooks, are translated past the stick allocating device on the continuous chain. An opposed pair of J-hook continuous chains co-operate with the stick allocating device so that opposed pairs of J-hooks receive single sticks from the stick allocating device and convey those sticks along the continuous chain over the lumber stack. The chains move linearly along an opposed pair of tracks supported above the lumber stack, the tracks supported conventionally by a support frame. The J-hook continuous chains are supported at either end of the opposed pair of tracks by sprockets, one of which is conventionally a drive sprocket, the other an idler sprocket.
Applicant is aware of prior art spacing stick depositing devices used in conjunction with conventional J-hook continuous chains, notably, Rysti, U.S. Pat. No. 3,823,834 which issued Jul. 7, 1974 for a "Method and Device for Performing the Insertion of Piling Strips in Timber Packages". The Rysti U.S. Pat. No. '834 method and device first stops the stick conveyor, then carrying hooks mounted on an elevated frame removes the sticks from the stick conveyor. The elevating frame is then lowered to the uppermost lumber tier where the sticks are pushed off the carrying hooks by a plurality of fingers so as to deposit the sticks on the lumber tier.
Applicant is also aware of Rysti, U.S. Pat. No. 4,360,303 which issued Nov. 23, 1982 for a "Method and Apparatus for Locating Spacer Strips between Layers of Timber Packages". The Rysti U.S. Pat. No. '303 method and apparatus also stops the stick conveyor at an appropriate position over a lumber stacks. The sticks are guided down onto the top surface of the uppermost tier of lumber by a plurality of free-fall depressors or plungers.
Applicant is further aware of Dion et al, U.S. Pat. No. 5,244,341 which issued on Sep. 14, 1993 for a Lath Placer. Dion et al teaches placing lath binders and stickers onto stacks of lumber using a rotating vacuum assisted delivery system for retrieval of lath from a curved magazine. A selectively actuable vacuum is applied to adhere the lath to the rotating delivery arm. Rotation of the delivery arm releases the lath onto the top surface of a lumber tier upon the selectively actuable vacuum being removed to allow the lath to fall, on edge, from the rotating arm.
It has been found that because spacing sticks or stickers are significantly thicker than lath, the Dion et al device will not necessarily place sticks flat but may place them so that they remain standing on edge. Further, it has been observed that dropping sticks from the transfer arm of the Dion et al device results in inaccurate placement of the sticks onto the stack of lumber. This is particularly problematic when attempting to place spacing sticks at the ends of the stack of lumber as the sticks may fall from the stack of lumber.
Consequently it is an object of the present invention to provide a device for the positive placement of spacing sticks onto a stack of lumber. In this regard Applicant is aware of U.S. Pat. No. 4,801,233 which issued to Ritola on Jan. 31, 1989 for a "Sticker Placer Apparatus" which teaches a device for the positive placement of spacing sticks onto a stack of lumber. Sticks are fed from a stick conveyor into inclined stick feeding pockets, the stick feeding pockets indexing individual sticks into the grip of actuable stick supporting and pinching arms rotatably mounted at the lowermost end of vertically translatable placement plungers. The vertical position of the placement plungers, and thus the position of the stick supporting and pinching arms, is governed in the Ritola device by an actuating arm releasing or increasing the tension on a flexible chain extending between the stick supporting and pinching arms and the actuating arm. Positive placement of a stick from the supporting and pinching arms is accomplished when the lowermost end of the vertically translatable placement plunger engages the top surface of a stack of lumber. Continuing detensioning of the flexible chain by the actuating arm allows the rotatably mounted stick support arm to rotate under the return biasing force of a resilient spring so as to deposit the stick from the support arm onto the stack of lumber.
In view of the complexity of the Ritola device, and in view of the fact that applicant is aware that the Ritola device is prone to jamming, it is an object of the present invention to provide a simple apparatus which may be retrofitted onto the support frames of conventional J-hook stick conveyors for the positive and accurate placing of spacing sticks onto a stack of lumber. Consequently a vacuum assisted stick retrieval and placement device is provided having two degrees of freedom, namely, a first radial or linear translation and a second rotational translation of a vacuum assisted stick gripping head.